In this Article

How does Caffeine work?

Caffeine works by stimulating the central nervous system (CNS), heart, and muscles. Caffeine also seems to improve the effectiveness of pain-relievers such as acetaminophen (Tylenol) and aspirin. Caffeine also works as a "water pill" to promote fluid loss.

Are there safety concerns?

Caffeine is safe for most adults. Caffeine can cause insomnia, nervousness and restlessness, stomach irritation, nausea and vomiting, increased heart rate and respiration, and other side effects. Caffeine can make sleep disorders in patients with acquired immunodeficiency syndrome (AIDS) worse. Larger doses might cause headache, anxiety, agitation, chest pain, and ringing in the ears. Large doses may be UNSAFE and can cause irregular heartbeats and even death.

Caffeine is probably safe in pregnant or breast-feeding women in daily amounts of less than 200 mg. This is about the amount in 1-2 cups of coffee. Consuming larger amounts during pregnancy might increase the chance of miscarriage and other potential negative effects.